Human Brain. Lateralization of Function. An extension of the spinal cord. Dr. Coulson Cognitive Science Department UCSD

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1 Lateralization of Function Human Brain An extension of the spinal cord Dr. Coulson Cognitive Science Department UCSD Cerebral Hemispheres Corpus Callosum Cerebral Lobes Neurons Brain composed of neurons 100 billion Neurons both send and receive signals to other cells in form of pulses Important parts Cell body Axon Synapse 1

2 Connectivity Each neuron connected to 10,000 other neurons Point of contact is the synapse Computing power of brain comes from connections Cortex Two millimeters thick and has area of 1.5 square meters Cartoon View: Frontal Lobe In front of central sulcus Motor control Decisions, judgments, emotions Language production Cartoon View: Parietal Lobe Behind central sulcus Perception of stimuli related to touch, pressure, temperature, pain Attention Spatial cognition Cartoon View: Temporal Lobe Below lateral fissure Visual perception, object recognition, auditory processing Memory Language comprehension Cartoon View: Occipital Lobe Located at back of brain, behind the parietal lobe and temporal lobe Vision 2

3 Lateralization of Function Motor Control One side of the brain is more crucial for a given function and/or more efficient at the underlying computational tasks Typically a matter of degree Strongly vs. Weakly Lateralized Motor control a good example of a lateralized function Sensorimotor Cortex What about language? Wada Test Language is a paradigmatic example of a lateralized cognitive phenomenon 3

4 Wada Test Lateralization of Function Most evidence of lateralized brain function comes from observing how brain damage affects behavior on various sorts of cognitive tasks Paul Broca 19 th century French neurologist Star patient: Leborgne Understood most of what was said to him Able to eat, drink (move mouth and tongue) Only utterance was tan Broca s Discovery Leborgne s brain had damage to the lower rear portion of frontal lobe, lower front portion of parietal lobe, and upper part of the temporal lobe Broca deemed frontal lobe damage most important Aphasia partial or total loss of ability to articulate ideas due to brain damage Broca s Area lower rear portion of frontal lobe, adjacent to motor cortex Inferior frontal gyrus Brodmann s Areas 44/45 Brodmann s Areas Korbinian Brodmann examined brain cells with various stains designed to detect chemical differences between areas Brain areas defined by cytoarchitectonic characteristics known as Brodmann s Areas 52 areas in the human brain (though some subdivided into a, b, etc) Broca s Aphasia M.E. Cinderella...poor...um 'dopted her...scrubbed floor, um, tidy...poor, um...'dopted...si-sisters and mother...ball. Ball, prince um, shoe... Examiner Keep going. M.E. Scrubbed and uh washed and un...tidy, uh, sisters and mother, prince, no, prince, yes. Cinderella hooked prince. (Laughs.) Um, um, shoes, um, twelve o'clock ball, finished. Examiner So what happened in the end? M.E. Married. Examiner How does he find her? M.E. Um, Prince, um, happen to, um...prince, and Cinderalla meet, um met um met. Examiner What happened at the ball? They didn't get married at the ball. M.E. No, um, no...i don't know. Shoe, um found shoe... 4

5 Broca s Patient Wernicke s Aphasia 1871 Karl Wernicke reported a different sort of language disorder Symptoms Talk fluently, excessively Use made up words Don t understand, in spite of intact hearing Wernicke s Area Wernicke s Area Wernicke s Aphasic C.B. Uh, well this is the... the /dodu/ of this. This and this and this and this. These things going in there like that. This is /sen/ things here. This one here, these two things here. And the other one here, back in this one, this one /gesh/ look at this one. Examiner: Yeah, what's happening there? C.B. I can't tell you what that is, but I know what it is, but I don't know where it is. But I don't know what's under. I know it's you couldn't say it's... I couldn't say what it is. I couldn't say what that is. This shu-- that should be right in here. That's very bad in there. Anyway, this one here, and that, and that's it. This is the getting in here and that's the getting around here, and that, and that's it. This is getting in here and that's the getting around here, this one and one with this one. And this one, and that's it, isn't it? I don't know what else you'd want. Describing a picture of a child taking a cookie 5

6 Wernicke s Patient Pop Quiz Wernicke s Aphasia (Temporal Lobe Lesions) Pop Quiz Broca s Aphasia (Frontal Lobe Lesions) Sex Differences Women more vulnerable to aphasia after damage to frontal lobe Men more vulnerable to aphasia after damage to parietal and temporal lobe areas Similar sex differences in apraxia, impairment in voluntary motions Wernicke-Geschwind Model Broca s Area stores motor representation of speech Wernicke s Area stores auditory representation of speech sounds Connected by fiber tract known as arcuate fasiculus Considered an oversimplified model Concepts Ventral prefrontal X cortex Motor word Arcuate Fasciculus Speech motor output Auditory word Broca s Aphasia Association Cortex Posterior Temporal Cortex Auditory input psychology.rutgers.edu/~rypma/ 6

7 Concepts Association Cortex Concepts Association Cortex Ventral prefrontal cortex Motor word XPosterior Temporal Auditory word Cortex Arcuate Fasciculus Ventral prefrontal cortex Motor word XArcuate Fasciculus Posterior Temporal Auditory word Cortex Speech motor output Auditory input Speech motor output Auditory input Wernicke s Aphasia psychology.rutgers.edu/~rypma/ Conduction Aphasia psychology.rutgers.edu/~rypma/ Wada Test Broca s Aphasia Reprise Wernicke s Aphasia Conduction Aphasia But remember, these models are cartoons 7